This invention relates to mechanical seals which may be used to separate a first liquid fluid from a second fluid. In the context of a pump, for example, the mechanical seal is mounted so as to extend between the pump shaft and the pump housing.
A mechanical shaft seal for separating a first liquid fluid from a second fluid includes a rotary assembly for mounting on a rotatable shaft for rotation therewith and a stationary assembly for securing to a fixed structure within which the rotary assembly is located. Such a seal includes a xe2x80x9cfloating componentxe2x80x9d which forms part of either the rotary or the stationary assembly and which is axially moveable relative to the rotatable shaft. In addition, the seal includes a xe2x80x9cstaticxe2x80x9d component which forms part of the other of the rotary and stationary assemblies, this component being axially fixed relative to the rotatable shaft. The floating component has a flat angular end face or seal face which is directed toward the static component, usually by means of one or more springs, to close the seal faces together to form a sliding face seal.
A seal with a floating component forming part of the rotary assembly is described as a rotary seal and a seal whose floating component forms part of the stationary assembly is referred to as a stationary seal.
If the sliding seal between the rotary and stationary components is assembled and pre-set prior to despatch from the manufacturer, the seal is referred to as a xe2x80x9ccartridge sealxe2x80x9d. If the rotary and stationary components are despatched in unassembled form from the manufacturer, the seal is a xe2x80x9ccomponent sealxe2x80x9d.
A mechanical seal may be single mechanical seal or a multiple mechanical seal, typically a double or triple mechanical seal. Furthermore a mechanical seal may include a barrier fluid system by means of which a third fluid, normally liquid, is fed to the seal and this third or barrier fluid acts to separate the first and second fluids and is intended to facilitate the removal of heat generated between the sliding seal faces, thereby helping to prolong the life of the seal.
In order for the barrier fluid system to be effective, the barrier fluid has to be fed to the seal and, within the seal, to one or more areas where cooling is to be effected and thence is fed away from the seal. This involves axial movement of the barrier fluid and to some extent this is affected by the forces induced as a result of the rotation of the rotary assembly relative to the stationary assembly.
The present invention is based on the discovery that there may be located within the seal a means for promoting or enhancing the actual movement of the barrier fluid along a desired flow path, which means may be effective regardless of the direction of rotation of the rotary assembly relative to the stationary assembly.
According to the present invention there is provided a mechanical shaft seal for separating a first liquid fluid from a second fluid comprising:
(a) a rotary assembly for mounting on rotatable shaft for rotation therewith:
(b) a stationary assembly for securing to a fixed structure within which the rotary assembly is located;
(c) said rotary assembly and said stationary assembly each carrying a respective mating sealing face;
(d) one of said seal faces being located on a floating component mounted for axial movement with respect to said shaft;
(e) means for urging the floating component in a direction toward the other of said seal faces;
(f) means for feeding a third fluid to a location within the seal which, when the seal is in use, lies between the first and second fluids; and
(g) means for promoting axial flow of said third liquid within the seal, said axial flow promoting means being arranged to promote said flow irrespective of the direction of rotation of the rotating assembly relative to the stationary assembly.
Preferably the axial flow promotion means comprises a member having a grooved, circumferentially extending face, at least one groove extending both axially and circumferentially in one direction about said face and at least one other groove extending both axially and circumferentially in the opposite direction about said face.
Accordingly the present invention provides the inducement of barrier fluid flow which is independent of the direction of rotation of the equipment of which the seal forms a part.
Preferably the grooves have a plan view angle relative to the longitudinal axis of the seal of between 1xc2x0 and 89xc2x0.
The base of at least one of the grooves may be inclined radially relative to the longitudinal axis of the seal. Additionally or alternatively, the face of the grooved member, between at least two grooves, may be inclined relative to the longitudinal axis of the seal.
The grooves may be circumferentially adjacent each other on the grooved member. Alternatively, at least one groove may be axially adjacent or separated from at least one other groove.
The groove member may form part of the rotary assembly. The fixed structure to which, in use, the stationary assembly is secured will include a housing having a component located radially outside grooved member, said component having an inner face which is inclined relative to the longitudinal axis of the seal.
Alternatively, the grooved member may form part of the stationary assembly or, in use, form part of the fixed structure to which the stationary assembly is attached.
Preferably the seal defines a space to which, in use, the third fluid is fed, there being located within said space means for dividing said space into two opposing flow paths for said third fluid.
The present invention may be applied to rotary and stationary seals whether they are of cartridge or component type.